This is a proposal to build and clinically test a transverse section tomographic positron camera for quantitative imaging of the heart in gated studies using positron emitters such as Rb82, Ga68 and F18. The system we have designed consists of a circular ring of 280 NaI(T1) crystals 8 mm X 30 mm X 50 mm. The crystals are read out by coded light pipes that permit complete data transfer with only 56 photomultipliers. This and other features lead to an economic design that permits 4 to 7 mm FWHM over a cylinder of diameter 40 cm. Digital image reconstruction will be performed on a small dedicated computer using algorithms already developed. The device is applicable for either static or dynamic imaging of the brain and other organs (approximately 10 sec per frame) as well as gated images of the heart (approximately 100 sec per transverse section). The major application is for the detection and understainding of cardiac and cerebral vascular disease and physiology.